低温低溶解氧海水环境中X70钢阴极极化行为研究

采用动电位极化曲线及恒电位极化法研究了X70管线钢在低温低溶解氧海水中的阴极极化行为,线性极化测试和表面分析技术分析了阴极保护后钙镁沉积层的形成情况.结果表明,8℃、1.5 mg/L溶解氧海水中X70管线钢的析氢电位最正,4℃、3.0 mg/L溶解氧海水中析氢电流密度最小.在低温低溶解氧海水中钙质层难以形成,要得到致密良好的钙质层需要较高的保护电位.低温低溶解氧海水条件有利于Mg（OH）₂沉积,对CaCO₃形成不利.

Cathodic Polarization Behavior of X70 Steel in Low Temperature and Low Dissolved Oxygen Seawater

Potentiodynamic polarization curves and potentiostatic polarization measurements were carried out to study the cathodic polarization behavior of X70 pipeline steel in low temperature and low dissolved oxygen seawater.The formation of the calcareous deposits after CP was analyzed by electrochemical linear polarization resistances and surface analysis techniques,SEM and EDX.The results showed that the hydrogen evolution potential of X70 steel was the most positive in seawater with 1.5 mg/L of dissolved oxygen at 8℃,the evolving hydrogen current density of X70 steel was the smallest in seawater with 3.0 mg/L of dissolved oxygen at 4℃.In low temperature and low dissolved oxygen seawater the formation of calcareous deposits on the steel was with difficulty,in otherwords,higher polarization potential was needed to form the compact calcareous deposits.In low temperature and low dissolved oxygen seawater,it favored the precipitation of Mg（OH）₂,but not the formation of CaCO₃.